I want to partition the card so I can use it for an OS install disk (Mac OS Extended GUID) in one partition and as a camera disk (MS-DOS FAT) in the other partition.

4. Make sure your 8GB or greater USB Stick/Drive/SD card is mounted. Choose partition and go. On a Retina MacBook Pro with a 8GB SD Card, the process took about 10- to 15 minutes.